John a



1 ing certain fibers. p

Qfore-the processes of bleaching with I invention any v manner than does UNITED STATES PATENT OFFICE.

PROCESS OF BLEACHING VEGETABLE TISSUES.

SPECIFICATION forming part of Letters Patent No. 303,065, dated August 5,1884.

l v I Application filed December 11, 1893.

' {*0 all whom, it hwyconcern.-

5 vented certain new and useful Improvements in Processes of Bleaching Vegetable Tissues, fullyidescribed and represented in the following specification.v

This invention consists, first, in the combination, with permanganate of potash for decomposing the coloring-matter, of oxalic acid and sulphite of sodium for removing the pre vious agent and the coloring-matter from the 1 tissues; and, also, in the combination of chlorine with the acid and sulphite of sodium in treatpermanga'nates have been deficient'in two important respectsnamely, that the agents used t discharge them from the tissues required to v be used in aconcentrated and injurious form,

or the tissues required repeated treatment with the various agents to effect such bleaching as'was desired. In either case the expense I of such processes deprived them of their practical value, and in all cases the tissues regained v a considerable part of the discharged color and especial-1y if upon exposure to the air, afiected by heat, as in calendering processes. Such processes could therefore be used only in the production of light-brown fibers, while my invention is intended-'toproduce permanently white tissues by the substitution of the a 1 oxalic-acid mixed with sulphite'of sodium for 35 the discharging agents heretofore used. I This invention is intended as a substitute for the bleaching processes usually practiced in -pulp;grinding engines, wherein from five to ten hundred pounds of pulp are acted on at once, and a period of eight to twelve ho is consumed in working the pulpthrough the bleaching-liquor. "In mills of large capacity from ten to twenty such engines, using from seventy-five to one hundred and fifty horse power, are employed all the time in'bleaching and washing the pulp, it being absolutely necessary to remove I every trace ,of the chlorine to prevent'yellow-ness in the product. In m can be bleached at one time in'a single vessel, I the chemicals acting in a. much more rapid pressure of steam may required amount of the ,stock chlorine, anda charge of (X0 specimens.)

five tons may therefore be bleached and washed in about five hours. The same amount operated upon in the ordinary pulping-engines would require the continuous use of thirty such engines for over twenty-four hours and JOHN A. SOUTHMAYD, OF ELIZABETH, ASSIGNOR TO HUMPHREY BLODG ETT l DUNHAM, OF NEWARK, NE? JERSEY.

the consumption of one hundred and fifty horse-power during the whole of such time. My invention, therefore, saves the spaceoccupied' by all this machinery, the power required to operate it, and four-fifths of all the time now consumed by its use.

The material to be bleached may first be treated with caustic potash to soften and prepare the tissues for the action of the permanganate of potash, and such treatment is best elfected in a close boiler, where the heat and be used to facilitate the mechanical and chemical action of opening the fibers. The permanganate attacks and decomposes the coloringmatter, but. does not remove it, such matter being subsequently removed by the use of the oxalic acid andsulphite of sodium.

I will first describe the application of the process to the bleaching of hard spruce, and

then state the modifications employed with- The 'first stage of the process 1 other fibers. consists in boiling the fibrous matter or tissue with a solution of permanganate of potash, in the proportion of ten to fifteen pounds of the agent to one ton of the fiber, until the. same appears to be thoroughlyoxidized, the open tion requiring from one to two hours it performed in'a closed vessel under steam=press ure,but aratherlonger time if boiled in an open vessel. Thc'applieation of heat in this stage of the process isessential to produce the required effect; but the subsequent treatment may be performed ina closed or open vessel without heat, as may bemost convenient.- When the fiber is properly permanganate,

the bleaching in about two hours bythe deafi'ected' by the. t I treat it with a solution of oxalic acid and sulphite of sodium, which effects compositionofthe permanganate and coloringmatter.

treatment 'suflices to discharge all the color;

but in cases where the fiber, owing'to its place i With' certain kinds of tissues this TOO bleached by such" same results can be obtained by using the acid without heat, if a longer time be allowed for its action. As the spruce fiber is very difiicult to bleach, other tissues can be whitened in a shorter time and with a smaller proporr 5 tion of the agents employed.

The advantage of my invention consists in its cheapness, owing to the small quantity of the agents required, and in the perfect results secured in the treatment of crude fibers, which 7 by my process may in a single operation be bleached ready for use in preparingperfectlywhite paper. As stated above, the'effect of k the permanganate can be best secured bythe agency of heat; but the subsequent treatment may. be performed either-hot, or, cold, as the operator. may have less or more time for the operation. Inv any case the savinglof time is "very great by the use of the process Lhave 'devised, for the reason that the ordinary ch10- 3 O rine' bleaches usually require a great deal of' time, both in'the application and action of the agent itself and in the tedious washings re- 1' quired to prevent the fibers from turning yel- 'low,'as is the case if the chlorine is not effectuallyremovedfrom the tissues. The economyof my process 'therefo're'consists largely in the reduction of time effected and the greatincrease of. capacity thereby added to the ves- 1 's'els or tanks already employed with other 4' agents.

T I am fully aware that the chlorinehas been used in various combinations, but find that'its effect, when combined directly with the acid and sulphite-of-sodium solution, is totallydif- 'ferent from that otherwise" obtained, as the three agents effect, with one-sixth the amount 7 of chlorine otherwise-used, a perfect removal of the coloring-matter already-combined with the permanganate ofpotash. Thus, a chlorine 5 bath of over 1 Baum would be required, if used alone to effect the bleaching, and a tedi-v ous process of soaking and washing to remove the chlorine in the end, while my process usuallyeffects the same results in a greatly diminished time without the use of chlorine, or with one-sixth the'amount of chlorine in the case 1 of certain tissues, as spruce fibers. The chlorine thus used is entirely removed from the tissues when washed to remove the oxalic acid I and sulphite of sodium, the three agents being removed together in a very shorttime, and the chlorine appearing to lose its distinctive illjll:

riousproperties when thus combined.

In treating manufactured fibers, as rags, I

find that, owing to the twisting of the threads ,2". and the variety of thicknesses, textures, and

colors which I subject to treatmeht at one time,'I am compelled to use nearly the same amount of chemicals as for hard crude fibers; but with soft'grasses and soft woodslike poplar I use only from seven to twelve pounds of permanganate, twenty five to thirtyfive pounds of acid, and seven to'twelve pounds of the sulphite of sodium for each ton of the tis-I I sues. I also find in practice that it requires. about sixteen hundred gallons of water to soak a ton of spruce fiber, and the preparatory boiling with potash, which prepares the fibers so peculiarly for the action of the permanganate, therefore requires that amount of water. When the alkali is drawn off before ,the bleaching operation, the bleaching a ents are then applied with the-waterin w ich't-hey are dis-- solved, and enough water is added to boil the charge thoroughly. v

- I am also aware that the permanganate of potash has been used heretofore in bleaching processes, but not in combinationwith the dis charging agents I employ, nor'with the closed 1 boiler, which prevents the dissipation of the 0 iactive agents, as when boiledin'the open air,

the most volatile elements beingthe most valuable in the bleaching process;

Iclain1 I 1. The process of. bleaching vegetable tis- )5 sues, which consists,-first, intreating the same with permanganate of potash to destroy the 'coloringnattenand, second, in neutralizing and removing the same bythe application of oxalic'acid and sulphite-bf sodium, substantially in themanner herein shown and described.

- 1 f 2. The process of; bleaching'vegetable tis sues, which consists, first, in treating the same with permanganate of potash-to destroy the 10-5. coloring-matter; secondly, in ne'ntralizing and removingthe same by the application-of oxalic acid,'sulphite of sodium; and chlorine, substantially as describedy'and, thirdly, in washing out the chlorine and discharging no agents, substantially as herein set forth.-

3..The process of bleaching-vegetablet is= T?- sues, which consists, first,-in boiling the same;

with potash under pressure in aclosed boiler; second, in removing the alkaline liquor and 111 5 boil-ing under pressure in the same vessel with "permanganate 0f potash; third-,in boiling the same with oxalic acid and-sulphite of sodium, substantially in the manner set forth. f 4. The process of bleachingvegetable tismo sues, consisting, first, in treating'thesamef withpermanganate of potash, and, second, in applying a mixture of oxalic acid, sulphite of sodium, and chlorine, substantiallyas and for the purpose set forth. a In testimony whereof I have hereunto set my 1 hand inthe presence of two subscribing witnesses; 11,

r JOHN-.A-SOUTHlWIAXD. 11 s \Vitnessesy M G; G. HERRIO'K,

THos, S. CRAN 

